The present invention relates to device and method for controlling supply of current and static capacitance to a compressor.
FIG. 1 illustrates a diagram showing a related art device for controlling supply of current and static capacitance to a compressor.
Referring to FIG. 1, a related art device for controlling supply of current and static capacitance to a compressor is provided with a utility power supply 1, a first relay 2 for being turned on/off in response to a control signal from the compressor, a reactor 3 for absorbing a reactive power from the utility power supplied through the utility power supply 1 according to the turning on/off operation of the first relay 2, and providing the utility power to a main winding C1 of a compressor motor xe2x80x98Mxe2x80x99, a second relay 4 for monitoring a voltage on the reactor 3, a first contact 4a connected parallel to the third reactor 3 for being opened or closed by the second relay 4, an operating capacitor 5 connected in parallel to the third reactor 3, a starting capacitor 6 connected in parallel with the operating capacitor 5, a third relay 7 for monitoring a voltage at starting, a second contact 7a fitted to a fore end of the second relay 4 for being opened or closed by the third relay, and a third contact 7b fitted to a rear end of the starting capacitor.
The operation of the foregoing related art device will be explained.
Upon application of the control signal from the compressor, the first relay 2 is turned on, to supply a power to the main winding C1 of the compressor motor xe2x80x98Mxe2x80x99 through the third reactor 3. In this instance, the third reactor 3 removes a reactive power from the power to the main winding. On the other hand, the utility power is supplied to a supplementary winding of the compressor motor xe2x80x98Mxe2x80x99 through the parallel circuit of the operating capacitor 5 and the starting capacitor 6 as the third contact 7b is closed. Referring to a region 8 in FIG. 1, at an initial starting of the compressor, since the compressor motor xe2x80x98Mxe2x80x99 is not rotated, a voltage to the third relay 7 is too low to put the third relay 7 into action. And, if the compressor motor xe2x80x98Mxe2x80x99 becomes to rotate at a revolution higher than a preset value as the voltage on the third relay 7 rises according to the rotation of the compressor motor xe2x80x98Mxe2x80x99, the third relay 7 comes into action, to close the second contact 7a and to open the third contact 7b. Since the second relay 4 comes into action as the second contact 7a is closed, the first contact 4a is closed to turn off the third reactor 3 and to open the third contact 7b, to isolate the starting capacitor from the circuit. That is, at the moment of starting, the third reactor 3 becomes to be connected to the compressor motor xe2x80x98Mxe2x80x99 in series to limit an excessive current, and the starting capacitor 6 provides a greater capacitance to the supplementary winding C2 to improve starting characteristics of the compressor.
However, the related art device for controlling supply of power to a compressor has the following disadvantages.
First, the re have been frequent troubles in the region 8 at which a starting capacitance is controlled.
Second, the mechanical system of the device for supplying power to the compressor costs high.
Third, the starting control by the voltage rise following rotation of the compressor motor xe2x80x98Mxe2x80x99 can not define a starting current accurately and has a poor starting characteristic.
Fourth, the generation of excessive current in starting of the compressor actuates the circuit breaker, gives bad influences to peripheral device of the compressor, and has inconvenience in restoring the compressor to an original state.
Accordingly, the present invention is directed to device and method for controlling supply of current and static capacitance to a compressor that substantially obviates one or more of the problems due to limitations and disadvantages of the related art
An object of the present invention is to provide device and method for controlling supply of current and static capacitance to a compressor, which can prevent flow of excessive current to a main winding of the compressor.
Other object of the present invention is to provide device and method for controlling supply of current and static capacitance to a compressor, which can supply a stable voltage to the compressor regardless of variation of an external utility voltage.
Another object of the present invention is to provide device and method for controlling supply of current and static capacitance to a compressor, which can prevent internal contacts suffer from damage caused by sharp current concentration during starting and operation of the compressor.
Further object of the present invention is to provide device and method for controlling supply of current and static capacitance to a compressor, which can make stable supply of current and static capacitance to the compressor to be consistent to an external temperature and season.
Still further object of the present invention is to provide device and method for controlling supply of current and static capacitance to a compressor, which can improve starting characteristics of the compressor of comparatively large capacity.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve the se and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, the device and method includes a controlling signal generating part for sensing a state of a utility voltage, i.e., a size and frequency of the utility voltage at first. Then, the controlling signal generating part classifies an operation time period into a starting time period and a time period after the starting time period, and generates a phase control signal for controlling a current to a main winding of the compressor to be different according to a result of comparison that the utility voltage being higher or lower than a preset value in starting. And, the control signal generating part provides a switching control signal for changing an internal circuit of the device in order to control a size of the utility voltage provided to the main winding and the stating supplementary winding of the compressor different in the starting and after the starting. And, the control signal generating part can generate the switching control signal and the phase control signal appropriately varying with an external temperature state of the compressors, seasons, and a present state of current supplied to compressor motors. The control signal generating part controls supply of the current of the utility voltage by controlling a phase thereof. The present invention suggests to use a triac or a negative temperature coefficient resister for controlling the phase of the current.
In the meantime, a current controlling part controls the phase of the current of the utility voltage in response to the phase control signal and changes an internal circuit in response to the switching control signal, for limiting the current of the utility voltage in supplying the current to the main windings in starting of the compressors, and supplying the current of the utility voltage to the main windings regularly after the starting.
In the meantime, a static capacitance controlling part changes an internal circuit in response to the switching control signal for supplying a starting static capacitance of the current from the current controlling part and an operating static capacitance of the current of the utility voltage to the supplementary winding in starting for starting the compressor effectively, and the operating static capacitance of the current of the utility voltage to the supplementary winding after the starting. The current controlling part and the static capacitance controlling part have switches respectively for varying the internal circuits in response to the control signals, and the control signal generating part generates the switching control signal different before and after the starting, in response to which the switches are operative in opposite directions.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.